Method for producing a seamless tubing

ABSTRACT

A method for producing a seamless tubing comprises extruding the thermoplastic material from extruder in the form of tubing in semi-molten condition, introducing the first compressed cooling medium into the tubing and radially spouting the fluid medium against the inner surface of the tubing wall for a certain distance thereby expanding the tubing into desired diameter and simultaneously cooling the tubing, and centripetally spouting the second compressed cooling fluid medium against the outer surface of the tubing wall simultaneously with the spout of the first fluid medium so as to sandwich the tubing wall by the both fluid medium for a certain distance. Further, an apparatus for the method comprises an extruder for extruding the thermoplastic material in the form of tubing in semi-molten condition, means for introducing the first compressed cooling fluid medium into the tubing, means for radially spouting the fluid medium against the inner surface of the tubing wall for a certain distance to expand and cool the tubing, means for centripetally spouting the second compressed cooling fluid medium against the outer surface of the tubing wall simultaneously with the spout of the first fluid medium so as to sandwich the tubing wall by the both fluid mediums for a certain distance, and means for continuously winding up the expanded, cooled tubing.

United States Patent [191 Kuroda METHOD FOR PRODUCING A SEAMLESS TUBING[76] Inventor: Shigeharu Kuroda, 1994-29,

Oshikuma-cho, Nara, Japan [22] Filed: May 5, 1970 [21] Appl. No.: 34,688

[52] US. Cl 264/89, 264/95, 264/209, 264/210 R, 264/237, 264/348 [51]Int. Cl. B29c 23/00, B290 25/00, B29d 23/04 [58] Field of Search264/209, 95, 237, 264/348, 40, 89, 210 R Primary Examiner-Robert F.White Assistant ExaminerJeffery R. Thurlow [57] ABSTRACT A method forproducing'a seamless tubing comprises June 26, 1973 extruding thethermoplastic material from extruder in the form of tubing insemi-molten condition, introducing the first compressed cooling mediuminto the tubing and radially spouting the fluid medium against the innersurface of the tubing wall for a certain distance thereby expanding thetubing into desired diameter and simultaneously cooling the tubing, andcentripetally spouting the second compressed cooling fluid mediumagainst the outer surface of the tubing wall simultaneously with thespout of the first fluid medium so as to sandwich the tubing wall by theboth fluid medium for a certain distance. Further, an apparatus for themethod comprises an extruder for extruding the thermoplastic material inthe form of tubing in semi-molten condition, means for introducing thefirst compressed cooling fluid medium into the tubing, means forradially spouting the fluid medium against the inner surface of thetubing wall for a certaindistance to expandand cool the tubing, meansfor centripetally spouting the second compressed cooling fluid mediumagainst the outer surface of the tubing wall simultaneously with thespout of the first fluid medium so as to sandwich the tubing wall by theboth fluid mediums for a certain distance, and means for continuouslywinding up the expanded, cooled tubing.

1 Claim, 4 Drawing Figures Patented June 26, 1973 3 Sheets-Sheet l 3-Sheets-Sheet Patented June 26, 1973 Patented June 2-6, 1973 3,742,105

3 Sheets-Sheet 3 1 METHOD FOR PRODUCING A SEAMLESS TUBING continuouslyextruded from the extruder in hot semimolten condition.

One object of the present invention is to provide a new and improvedmethod for producing the thinwalled seamless tubing continuously andrapidly.

Another object of the present invention is to provide an unique coolingsystem for the plastic material which is extruded from the die head ofthe extruder in hot semi-molten condition in the form of tubing.

in carrying out the invention in one aspect, a method for producing aseamless tubing is provided in which the process comprises the steps ofextruding the thermoplastic material from extruder in the form of tubingin semi-molten condition, introducing the first compressed coolingmedium into the tubing and radially spouting the fluid medium againstthe inner surface of the tubing wall for a certain distance therebyexpanding the tubing into desired diameter and simultaneously coolingthe tubing, and centripetally spouting the second compressed coolingfluid medium against the outer surface of the tubing wall simultaneouslywith the spout of the first fluid medium so as to sandwich the tubingwall by the both fluid medium for a certain distance,

. thereby cooling the tubing sufficiently and rapidly.

Preferably, the first and the second fluid mediums are continuous streamof air and being maintained at settled pressure and temperature.

Further the apparatus for performing this improved method has been builtand being in successful operation.

The apparatus comprises an extruder for extruding the thermoplasticmaterial in' the form of tubing in semi-molten condition, means forintroducing the first compressed cooling fluid medium into the tubing,means for radially spouting the fluid medium against the inner surfaceof the tubing wall for a certain distance to expand and cool the tubing,means for centripetally spouting the second compressed cooling fluidmedium against the outer surface of the tubing wall simultaneously withthe spout of the first fluid medium so as to sandwich the tubing wall bythe both fluid mediums for a certain distance, and means forcontinuously winding up the expanded, cooled tubing.

Other objects and advantages of the subject invention will becomeapparent from reading the following detailed description and byreference to the accompanying drawings wherein:

FIG. 1 is a cross-sectional view of the apparatus according to thepresent invention;

FIG. 2 is a vertical sectional view of the apparatus taken along theline 2--2 in FIG. 1;

FIG. 3 is a cross-sectional view of other embodiment of the apparatus;and

FIG. 4 is a side elevational view, on a reduced scale, of an anotherembodiment of the apparatus according to the present invention.

Referring now to the drawings wherein like numerals have been employedto designate similar parts throughout the various figures, it will beseen that one embodiair may be critically controlled to expand thetubing ment of the apparatus according to the present invention isillustrated by the numeral (A)..

The apparatus includes an extruder 10 having a die head 11 and a feedingscrew 12 which is rotated within abarrel 13 by any suitable drive meansv(not shown). The extruder 10 which may be jacketed for a temperaturecontrolling medium in the usual way, extrudes the thermoplasticmaterial, for example, as polyethylene, polypropylene, polystyrene orthe like through the die head 11 out of a ring-like opening or orifice14 through which the molten or semi-molten mass emarges in hotthermoplastic condition in the form of tubing 15. Said die head 11 isprovided with a laterally elongated, double-wall tube or duct 16 whichis movably supported by the die head and which is coaxially arrangedwith the orifice 14 within the latter, the greater part of the tubebeing forwardly projected out of the die head. said double-wall tube 16comprises an inner wall 17 to define an inner passageway 18 therein, anouter wall 22 spaced apart from the inner wall to define a space orpassageway 20 therebetween. The passageway 20 between the walls isconnected to any source of compressed air, such as a variable speed pump21 driven by a suitable motor 23. This pump is of the positive deliverytype, such as a gear pump, and may be critically adjusted to deliver thedesired quantity of air at the desired pressure. The pressure isindicated on a pressure gage 24 in a connecting line 25, leading fromthe pump 21 to a passageway 20. Outer wall 22 is provided a number ofradial nozzles 26 at exposed portion thereof to spout the compressed,cooling air radially and outwardly.

Around the exposed portion of the double-wall tube 16, an outerdouble-walled cylinder 27 is arranged so as to leave a space or path 28for passing the extruded tubing 15. Said outer cylinder also is providedwith a passageway 29 between an inner and an outer walls 30 and 31thereof, the passageway also being communicated with the source of thecompressed air or speed pump 21 via a connecting line 32 which has apressure gage 57 for indicating the pressure of air. Said inner wall 30is provided with a number of nozzles 33 to spout compressed cooling airinwardly and radially. Preferably the compressed air to be spouted fromthe nozzles 26 and 33 is suitably cooled at a heatexchanger 56.

The thermoplastic tubing 15 is extruded in jsemimolten condition andpasses in the path 28 at which the tubing is subjected to expansion dueto the internal pressure of air spouted from the nozzles 26 and issimultaneously rapidly cooled by virtue of the internal air and theouter air which is spouted from the nozzles 33. The internal air withinthe tubing 15 flows into the inner passageway 18 through an end opening34 and is drawn off via an outlet 35 having an adjustable baffle plate36. By adjusting the baffle plate 36 and/or output of the variable speedpump 21, the internal pressure of into the desired diameter andcondition. Once the amount as to volume and pressure of air has been es-The cooled tubing, now emerged from an exit 41 of the path 28, is pulledby means of rotating pull rolls 37 and 38 which collapse the tubing intoa flattened sheet, these rolls also serving to eliminate any air in theflattened tubing. Theflatten'ed tubing designated 39 leaves the rolls ina flat ribbon-like form and is delivered to a wind roll 40 which may bedriven in any desired way, so that the flattened tubing is continuouslywound up by the wind roll 40. Prior to the winding stage, suitabletreatment such as printing, sealing or the like may be added to thetubing if desired.

To facilitate the withdrawal of the tubing up to the exit 41 of the path28 in the initial stage of the extrusion, the cylinder 27 is dividedinto two half parts, that is, an upper and a lower parts 42 and 43,these being separably hinged together at one of matting edges 42A and43A thereof by means of a hinge 44. By reason of this construction, theupper part 42 may be widely opened relative to the lower part 43 aroundthe hinge 44, whereby a leading end of the tubing being extruded fromthe orifice 14 at the initial stage of extrusion can be easilyintroduced up to the exit 41 of the path 28 by hands of operator,further this serves to facilitate the cleaning of interior of thecylinder 27 and the outer surface of the extended tube 16.

FIG. 3 showsan another embodiment of the present invention in which, forthe purpose of cooling the compressed air within the passageways intodesired temperature by fluid cooling medium, heat exchanging means areprovided within the air passageways, respectively. For purposes ofillustration, the fluid. is hereinafter represented as being a liquid.In the embodiment, the cylinder 27 is provided with an exchanger duct 50along the air passageway 29, for continuously passing the coolingliquid. This continuous cooling liquid is introduced from a suitablesource (not shown) through an inlet 51 and is vented out from an outlet52. Similar tothe above construction, the tube 16 also is provided withan exchanger duct 53, along theair passageway '18, for-continuouslypassing the cooling liquid, the latter being introduced from the sourcethrough an inlet 54 and' being vented out from an outlet 55.

It will be apparent that many modifications and variations can be madeto the embodiment of the invention described hereinbefore. For example,the orifice of the die head may be directed upward or downward, and themeans for expanding and cooling the extruded tubing, that is, theassemble consisted of the double-walled tube 16 and the outer cylinder27 may be vertically arranged.

invention also may be adapted for a double-wall tubing.

extruded from a dual orifice of the die head, instead of the single walltubing.

The subject invention in its broader aspects is not limited only to thespecific embodiments shown and described but departures may be madetherefrom within the scope of the accompanying claims without departingfrom the principles of the invention and without sacrificing its chiefadvantages.

What I claim is:

1. A method of producing a seamless tubing comprising extruding athermoplastic material from an extruder in the form of a semi-moltentubing, introducing a first compressed cooling fluid medium into thetubing and radially directing said first fluid medium outwardlyonto theinner surface of the tubing for a predetermined distance therebyexpanding the tubing to a desired diameter, the first fluid medium beingdirected successively from a plurality of longitudinally and radiallyspaced nozzles provided on an elongated inner-cylindrical wall having asubstantial length along the travelling direction of the tubing,centripetally directing a second compressed cooling fluid mediumradially inwardly onto the outer surface of the tubing when the tubingreaches its desired diameter while continuing the directing of the firstcompressed cooling fluid medium, the second fluid medium being directedsuccessively from a plurality of longitudinally and radially spacednozzles provided on an elongated outer cylindrical wall having asubstantial length along the travelling direction of the tubing,equalizing the pressure of the first fluid medium exerted onto the innersurface of the tubing with the pressure of the second fluid mediumexerted onto the outer surface of the tubing to fix the inner and outerdiameters'of the tubing, pulling the tubing axially through the spacedefined by the inner and outer cylindrical walls through a pair ofrotating pull rolls by a wind roll provided at the tinalend ofthetravelling direction ofthe tubing, collapsing the tubing into aflattened sheet by said pull rolls and winding the flat tened tubing.

i t I t

1. A method of producing a seamless tubing comprising extruding athermoplastic material from an extruder in the form of a semimoltentubing, introducing a first compressed cooling fluid medium into thetubing and radially directing said first fluid medium outwardly onto theinner surface of the tubing for a predetermined distance therebyexpanding the tubing to a desired diameter, the first fluid medium beingdirected successively from a plurality of longitudinally and radiallyspaced nozzles provided on an elongated inner cylindrical wall having asubstantial length along the travelling direction of the tubing,centripetally directing a second compressed cooling fluid mediumradially inwardly onto the outer surface of the tubing when the tubingreaches its desired diameter while continuing the directing of the firstcompressed cooling fluid medium, the second fluid medium being directedsuccessively from a plurality of longitudinally and radially spacednozzles provided on an elongated outer cylindrical wall having asubstantial length along the travelling direction of the tubing,equalizing the pressure of the first fluid medium exerted onto the innersurface of the tubing with the pressure of the second fluid mediumexerted onto the outer surface of the tubing to fix the inner and outerdiameters of the tubing, pulling the tubing axially through the spacedefined by the inner and outer cylindrical walls through a pair ofrotating pull rolls by a wind roll provided at the final end of thetravelling direction of the tubing, collapsing the tubing into aflattened sheet by said pull rolls and winding the flattened tubing.